Surface hardened cast iron article of manufacture



Patented Sept. 4, 1934 1,972,082 4 SURFACE HARDENED CAST IRON ARTI OF MANUFACTURE Marie Louis Andre Babinet,

Boulogne-sur- Seine, France, assignor, by mesne assignments, to The Nitricastiron Corporation, a corporation of Delaware No Drawing. Applicatio'nJune 13, 1931,

Serial'No. 544,291

8 Claims. (01148-31 My invention relates to the surface hardening of articles made of cast iron alloys, the hardening being efiected by the action of nitrogencontaining compounds, for example, ammonia.

It is known that'certain cast iron alloys may be hardened on their surface portions by subjecting them to a nitriding-treatment, i.'e. by heating an article made therefrom at a moderate temperature in contact with ammonia or ansiderable period oftime. So far as I am aware,

all of the cast iron alloys heretofore used for' Carbon 2.0 to 4% other nitrogen-liberating compound for a con ing a hardness of "180. The nitriding treatment applied in both cases consisted inheating the casting in the presence of ammonia gas for a period of hours at 500 C.

In cases where it is desired that the castings produced shall be easily machinable either in their'natural or as cast condition, or after a suitable heat treatment preliminary to the nitriding operation, the silicon content should be raised, so that it will about equal or exceed the percent- 5 age of chromium or of chromium and tungsten when the latter is also present.

In nitriding articles made from alloys within the foregoing range of proportions, it is advan- "tageous to subject the article to a preliminary heat treatment to bring the metal into the sorbitic state. This result may be obtained by heating the article to a temperature of around 950 C. and then quenching in a salt bath that has been heated to about 200 C. This treatment may be Manganese Up to 1% Silinn'n 1 t0 4% Chromium 1.5 to 3.5% 30 with the balance principally iron. Tungsten may be present in a proportion not exceeding 2%, and as further additions upto 1% each of one or more of the elements titanium, vanadium and molybdenum may be present.

While these alloys do not acquire as high a surface hardness by 'nit'riding as do alloys containing aluminum, it is easy to prepare them and to produce castings therefrom. The following are representative examples of alloys coming within the present invention:

o)- g (b) Carbon mm) a a 3117 Combined carbo 2.3% 1 mi 4 Silicon 1.20% 1.547

anganese-- 10% 11% Chromium"--- 1757 1. 91% Tifnnlnm 0 Vanadium... .45 0 '1- d 1. a a o Molybdenum .25 o "50 Ir I Balance.

. Alloy (a) showed a hardness before n'ltridlng of 490 Vickers-Brinell and after nitriding a hardness of 710. Alloy (b) showed a hardness before .55 nitriding of 424 Vlckers-Brinell and after nitride balance substantially all iron.

followed by a re-heating treatment at alower temperature if desired, although ordinarily the heating necessary to effect the nitriding will bring about such further change in the internal structure of the metal as may be desired.

I claim:

1. An article hardened in its surface portions by nitriding and consisting of an aluminum-free cast irorrhailloy containing fro1n 2.0 to 4% of carbon, of w ch a part is present in combined form, 5 from 1.5 to 3.5% of chromium, and from 1 to 4% of silicon with the balance substantially all iron.

2. An article hardened in its surface portions by nitriding and consisting of an aluminum-free cast iron alloy containing from 2.0 to 4%. of carbon, of which a part is present in combined form,

from 1.5 to 3.5% of chromium, from 1 to 4% of silicon, and an effective and substantial amount but not exceeding about 1% each of the metals titanium, vanadium and molybdenum, with the 95 3. An article hardened in its surface portions by nitriding and consisting of an aluminum-free cast iron alloy containing from 2.0 to 4% of carbon, of which a part is present in combined form, 1 from 1.5 to 3.5% of chromium, from 1 to 4% of. silicon, and an effective and substantialv amount but not exceeding about 1% of a metal from the group consisting of titanium, vanadium and molybdenum, with the balance substantially all 1 5 iron.

4. An article hardened in its surl'aceportions 'by nitrid-ing and consisting of an aluminum-free cast iron alloy containing from 2.0 to 4% of carbon, of which a part is present in combined 2 form, from 1.5 to 3.5% of chromium, irom 1 to 4% of silicon, and an effective and substantial amount but not exceeding about 2% of tungsten,

with the balance substantially all iron. I

5. An article hardened in its surface portions by nitriding and consisting of an aluminum-free cast iron alloy containing from 2.0 to 4% of carbon, of which a part is present in combined form, from 1.5 to 3.5% of chromium, from 1 to 4% of silicon, an efiective and substantial amount but not exceeding about 2% of tungsten, and an eflective and substantial amount but not exceeding about 1% of a metal from the group consisting of titanium, vanadium and molybdenum, with form, from 1.5 to 3.5% of chromium, from 1 to 4% of silicon, and an eflective and substantial amount but not exceeding about 1% ct manganese, with the balance substantially all iron.

'7. An article hardened in its surface portions by nitriding and consisting of an aluminum-free cast iron alloy containing about 3.32% carbon, oiwhich a part is present in combined form, about 1.20% silicon, about 0.70% manganese, about 1.75% chromium, about .26% titanium, about .45% vanadium and about 1.65% tungsten.

8. An article hardened in its surface portions by nitriding and consisting of an aluminum-tree cast iron alloy containing about 3.39% carbon, of which a part is present in combined form, about 1.54% silicon, about 31% manganese, about 1.91% chromium and about 0.25% molybdenum. 

